A conventional dead bolt secures a movable barrier, such as a patio door, in a closed position relative to a barrier frame, such as a patio door frame. To secure a patio door in the closed position, a user typically extends the dead bolt from a patio door frame-mounted dead bolt housing into an aligned aperture in the patio door thereby preventing movement of the patio door relative to the door frame.
These conventional dead bolts suffer from at least two disadvantages from a security awareness perspective. First, the dead bolt must be visually inspected to determine whether it is extended into and securely positioned within the aligned aperture. Second, the dead bolt assembly must be visually inspected to determine whether it has been tampered with, including removal of the dead bolt housing from the barrier frame or damage to the dead bolt itself, such as by removal of a portion of the dead bolt.
The dead bolt described in U.S. Pat. No. 3,803,575 to Gotanda is an attempt to solve the problem of providing without visual inspection an indication of whether a dead bolt is extended into and securely positioned in an aligned aperture. Gotanda describes a door-mounted dead bolt supporting a magnet and a door frame-mounted reed switch positioned adjacent an aperture that is aligned with and receives the extended dead bolt. The reed switch is activated into the "on" position by the magnet in the dead bolt, indicating a closed position of the door, when the dead bolt is extended into the aperture and the magnet is positioned adjacent the reed switch.
The Gotanda dead bolt suffers from at least two disadvantages. First, the Gotanda dead bolt requires installation of components on the door and on the door frame, resulting in expensive installation costs and possible future misalignment problems between the dead bolt and the reed switch. Second, the Gotanda dead bolt assembly must be visually inspected to determine whether it has been tampered with by removal of the reed switch from the door frame, removal of the dead bolt housing from the door, or damage to the dead bolt housing itself by removal of a portion of the dead bolt housing or removal of the dead bolt from the housing.
Accordingly, a need exists for an alarm switch assembly that secures a barrier within a barrier frame without the disadvantages of the prior art.